/Engine/Source/Runtime/Core/Public/GenericPlatform/GenericPlatformOutputDevices.h
Returns the absolute log filename generated from the project properties and/or command line parameters. The returned value may change during the execution, may not exist yet or may be locked by another process. It depends if the function is called before the log file was successfully opened or after. The log file is open lazily.
static [FString](API\Runtime\Core\Containers\FString) GetAbsoluteLogFilename()